1. Field of the Invention
This invention generally relates to a method and apparatus for continuously and selectively applying surface coatings and/or reinforced regions to a fiber batt to form a duct liner, duct wrap, dust board or similar product in which the exposed surfaces are provided with a suitable coating.
2. Description of the Prior Art
It is a well known to use a layer or batt of fiberglass, polymeric fiber or combination of fibers as an internal liner for sheet metal ductwork in heating, ventilating and air conditioning applications. Such liners insulate the ductwork to maintain the temperature of the air passing through the duct and, during cooling operations, to prevent condensation on exterior surfaces of the duct. These batts, can also can provide efficient sound absorption to control or decrease noise transmission within ductwork or in other applications. Particularly for batts used as duct liners, an interior surface of the liner will be exposed, at least periodically, to high velocity air flow. As a result, various federal, state, local and trade association regulations mandate that such liners meet certain standards.
One of the standards the liner must typically meet requires a certain resistance to erosion or degradation caused by the air flow through the duct. Such standard typically require that duct liners shall not break, flake, delaminate or otherwise erode at air flow velocities representing the greater of a specified multiple of the rated velocity or some minimum velocity. In order to accommodate such standards, manufacturers of such duct liners typically coat at least the major surface of the fiber batt that will be exposed to the air with one or more layers of materials that will prevent degradation of the underlying batt. Such layers may comprise a rubber or polymeric material that, when cured, forms a tough protective skin on the treated surface. Similarly, a fabric layer may be attached to the surface either singly or in combination with one or more underlying layers.
The coatings used in conjunction with duct liners have included a variety of elastomeric aqueous cross-linkable emulsion compositions such as acrylic emulsions. Typically, these elastomeric cross-linkable compositions are frothed or foamed prior to being applied to the fiber batt or other insulating sheet in order to provide a generally uniform coating on at least one major surface of the insulation. When the coating is heat cured, the emulsion coating composition is heated to a temperature and for a duration sufficient to evaporate the majority of the water and cause the frothed or foamed coating to collapse (i.e., coalesce and lose bubbles from the froth or foam). Heat curing also causes the elastomeric resins to cross link to form a thin protective coating.
Examples of such coating processes are provided in U.S. Pat. No. 4,990,370, issued Feb. 5, 1991, On-Line Surface and Edge Coating of Fiber Glass Duct Liner; U.S. Pat. No. 5,211,988, issued May 18, 1993, Method for Preparing a Smooth Surfaced Tough Elastomeric Coated Fibrous Batt; and U.S. Pat. No. 5,487,412, issued Jan. 30, 1996, Glass Fiber Airduct With Coated-Interior Surface Containing a Biocide. An example of a multilayer coating process is provided in U.S. application U.S. Ser. No. 2001/0033926, published Oct. 25, 2001.
These duct liners and other insulation products are typically provided by the manufacturers in rolls of approximately 100 feet in length and in a variety standard widths ranging between two and five feet. The duct manufacturers, in turn, attach the duct liner to a sheet metal surface with the coated side exposed and then trims the sheet metal and duct liner combination to standard widths and lengths that are then bent and formed into duct work with the duct liner providing the interior surface.
In some instances, however, the edges of the batt are not coated and in other instances, the trimming and forming creates an uncoated edge on the duct liner batt. In such instances, the uncoated surfaces represent areas that would be more prone to erosion, requiring the duct manufacturers and installers to coat or otherwise seal the exposed batt to comply with the relevant standards. Frequently this additional coating was applied during duct manufacturer after the initial forming of the sheet metal to produce a series of L-shaped duct portions. These duct portions can then be stacked to expose the uncoated edges and an adhesive or other sealant composition applied manually using a spray gun, brush, or roller. This practice, however, requires additional labor and handling by the duct manufacturer and can lead to visually unattractive results, varying coating quality, and environmental concerns. Further, such manually applied coatings may not, in fact, be sufficient to satisfy the applicable performance standards.
Another alternative is to supply batt users, particularly users such as HVAC duct and vehicle manufacturers, with a wider range finished batt widths to reduce the need for trimming batts to ensure an appropriate fit. This approach, however, complicates the ordering, manufacturing and inventory systems associated with Just-In-Time (JIT) by increasing the number of parts that have to be tracked.
The present invention provides a continuous and flexible method and apparatus for applying a coating material to portions of a fiber batt that may become an exposed surface in a subsequent application. The present invention provides for the selective coating of both major surfaces and actual or potential edge surfaces, thereby improving both the manufacturing process and the consistency and flexibility of the resulting product by reducing or eliminating the need for manual coating of unfinished edge surfaces.